
package com.vanda.exception;

/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002-2003 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
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 *    notice, this list of conditions and the following disclaimer in
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 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution, if
 *    any, must include the following acknowledgement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgement may appear in the software itself,
 *    if and wherever such third-party acknowledgements normally appear.
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 *
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 * <http://www.apache.org/>.
 */
import java.io.PrintStream;
import java.io.PrintWriter;
import java.io.Serializable;
import java.io.StringWriter;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;

/**
 * <p>A shared implementation of the nestable exception functionality.</p>
 * <p>
 * The code is shared between 
 * {@link org.apache.commons.lang.exception.NestableError NestableError},
 * {@link org.apache.commons.lang.exception.NestableException NestableException} and
 * {@link org.apache.commons.lang.exception.NestableRuntimeException NestableRuntimeException}.
 * </p>
 * 
 * @author <a href="mailto:Rafal.Krzewski@e-point.pl">Rafal Krzewski</a>
 * @author <a href="mailto:dlr@collab.net">Daniel Rall</a>
 * @author <a href="mailto:knielsen@apache.org">Kasper Nielsen</a>
 * @author <a href="mailto:steven@caswell.name">Steven Caswell</a>
 * @author Sean C. Sullivan
 * @author Stephen Colebourne
 * @since 1.0
 * @version $Id: NestableDelegate.java,v 1.6 2004/06/04 05:43:45 steveebersole Exp $
 */
public class NestableDelegate implements Serializable {

	/**
	 * Constructor error message.
	 */
	private static final String MUST_BE_THROWABLE =
		"The Nestable implementation passed to the NestableDelegate(Nestable) "
			+ "constructor must extend java.lang.Throwable";

	/**
	 * Holds the reference to the exception or error that we're
	 * wrapping (which must be a {@link
	 * org.apache.commons.lang.exception.Nestable} implementation).
	 */
	private Throwable nestable = null;
    
	/**
	 * Whether to print the stack trace top-down.
	 * This public flag may be set by calling code, typically in initialisation.
	 * @since 2.0
	 */
	private static boolean topDown = true;
    
	/**
	 * Whether to trim the repeated stack trace.
	 * This public flag may be set by calling code, typically in initialisation.
	 * @since 2.0
	 */
	private static boolean trimStackFrames = true;

	/**
	 * Constructs a new <code>NestableDelegate</code> instance to manage the
	 * specified <code>Nestable</code>.
	 *
	 * @param nestable the Nestable implementation (<i>must</i> extend
	 * {@link java.lang.Throwable})
	 * @since 2.0
	 */
	public NestableDelegate(Nestable nestable) {
		if (nestable instanceof Throwable) {
			this.nestable = (Throwable) nestable;
		} 
		else {
			throw new IllegalArgumentException(MUST_BE_THROWABLE);
		}
	}

	/**
	 * Returns the error message of the <code>Throwable</code> in the chain
	 * of <code>Throwable</code>s at the specified index, numbererd from 0.
	 *
	 * @param index the index of the <code>Throwable</code> in the chain of
	 * <code>Throwable</code>s
	 * @return the error message, or null if the <code>Throwable</code> at the
	 * specified index in the chain does not contain a message
	 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
	 * negative or not less than the count of <code>Throwable</code>s in the
	 * chain
	 * @since 2.0
	 */
	public String getMessage(int index) {
		Throwable t = this.getThrowable(index);
		if ( Nestable.class.isInstance(t) ) {
			return ( (Nestable) t ).getMessage(0);
		} 
		else {
			return t.getMessage();
		}
	}

	/**
	 * Returns the full message contained by the <code>Nestable</code>
	 * and any nested <code>Throwable</code>s.
	 *
	 * @param baseMsg the base message to use when creating the full
	 * message. Should be generally be called via
	 * <code>nestableHelper.getMessage( super.getMessage() )</code>,
	 * where <code>super</code> is an instance of {@link
	 * java.lang.Throwable}.
	 * @return The concatenated message for this and all nested
	 * <code>Throwable</code>s
	 * @since 2.0
	 */
	public String getMessage(String baseMsg) {
		StringBuffer msg = new StringBuffer();
		if (baseMsg != null) {
			msg.append(baseMsg);
		}

		Throwable nestedCause = ExceptionUtils.getCause(this.nestable);
		if (nestedCause != null) {
			String causeMsg = nestedCause.getMessage();
			if (causeMsg != null) {
				if (baseMsg != null) {
					msg.append(": ");
				}
				msg.append(causeMsg);
			}

		}
		return (msg.length() > 0 ? msg.toString() : null);
	}

	/**
	 * Returns the error message of this and any nested <code>Throwable</code>s
	 * in an array of Strings, one element for each message. Any
	 * <code>Throwable</code> not containing a message is represented in the
	 * array by a null. This has the effect of cause the length of the returned
	 * array to be equal to the result of the {@link #getThrowableCount()}
	 * operation.
	 *
	 * @return the error messages
	 * @since 2.0
	 */
	public String[] getMessages() {
		Throwable[] throwables = this.getThrowables();
		String[] msgs = new String[throwables.length];
		for (int i = 0; i < throwables.length; i++) {
			msgs[i] = Nestable.class.isInstance(throwables[i]) ?
					( (Nestable) throwables[i] ).getMessage(0) :
					throwables[i].getMessage();
		}
		return msgs;
	}

	/**
	 * Returns the <code>Throwable</code> in the chain of
	 * <code>Throwable</code>s at the specified index, numbererd from 0.
	 *
	 * @param index the index, numbered from 0, of the <code>Throwable</code> in
	 * the chain of <code>Throwable</code>s
	 * @return the <code>Throwable</code>
	 * @throws IndexOutOfBoundsException if the <code>index</code> argument is
	 * negative or not less than the count of <code>Throwable</code>s in the
	 * chain
	 * @since 2.0
	 */
	public Throwable getThrowable(int index) {
		if (index == 0) {
			return this.nestable;
		}
		Throwable[] throwables = this.getThrowables();
		return throwables[index];
	}

	/**
	 * Returns the number of <code>Throwable</code>s contained in the
	 * <code>Nestable</code> contained by this delegate.
	 *
	 * @return the throwable count
	 * @since 2.0
	 */
	public int getThrowableCount() {
		return ExceptionUtils.getThrowableCount(this.nestable);
	}

	/**
	 * Returns this delegate's <code>Nestable</code> and any nested
	 * <code>Throwable</code>s in an array of <code>Throwable</code>s, one
	 * element for each <code>Throwable</code>.
	 *
	 * @return the <code>Throwable</code>s
	 * @since 2.0
	 */
	public Throwable[] getThrowables() {
		return ExceptionUtils.getThrowables(this.nestable);
	}

	/**
	 * Returns the index, numbered from 0, of the first <code>Throwable</code>
	 * that matches the specified type in the chain of <code>Throwable</code>s
	 * held in this delegate's <code>Nestable</code> with an index greater than
	 * or equal to the specified index, or -1 if the type is not found.
	 *
	 * @param type <code>Class</code> to be found
	 * @param fromIndex the index, numbered from 0, of the starting position in
	 * the chain to be searched
	 * @return index of the first occurrence of the type in the chain, or -1 if
	 * the type is not found
	 * @throws IndexOutOfBoundsException if the <code>fromIndex</code> argument
	 * is negative or not less than the count of <code>Throwable</code>s in the
	 * chain
	 * @since 2.0
	 */
	public int indexOfThrowable(Class type, int fromIndex) {
		if (fromIndex < 0) {
			throw new IndexOutOfBoundsException("The start index was out of bounds: " + fromIndex);
		}
		Throwable[] throwables = ExceptionUtils.getThrowables(this.nestable);
		if (fromIndex >= throwables.length) {
			throw new IndexOutOfBoundsException("The start index was out of bounds: "
				+ fromIndex + " >= " + throwables.length);
		}
		for (int i = fromIndex; i < throwables.length; i++) {
			if ( throwables[i].getClass().equals(type) ) {
				return i;
			}
		}
		return -1;
	}

	/**
	 * Prints the stack trace of this exception the the standar error
	 * stream.
	 */
	public void printStackTrace() {
		printStackTrace(System.err);
	}

	/**
	 * Prints the stack trace of this exception to the specified
	 * stream.
	 *
	 * @param out <code>PrintStream</code> to use for output.
	 * @see #printStackTrace(PrintWriter)
	 */
	public void printStackTrace(PrintStream out) {
		synchronized (out) {
			PrintWriter pw = new PrintWriter(out, false);
			printStackTrace(pw);
			// Flush the PrintWriter before it's GC'ed.
			pw.flush();
		}
	}

	/**
	 * Prints the stack trace of this exception to the specified
	 * writer. If the Throwable class has a <code>getCause</code>
	 * method (i.e. running on jre1.4 or higher), this method just 
	 * uses Throwable's printStackTrace() method. Otherwise, generates
	 * the stack-trace, by taking into account the 'topDown' and 
	 * 'trimStackFrames' parameters. The topDown and trimStackFrames 
	 * are set to 'true' by default (produces jre1.4-like stack trace).
	 *
	 * @param out <code>PrintWriter</code> to use for output.
	 */
	public void printStackTrace(PrintWriter out) {
		Throwable throwable = this.nestable;
		// if running on jre1.4 or higher, use default printStackTrace
		if ( ExceptionUtils.isThrowableNested() ) {
			if (throwable instanceof Nestable) {
				( (Nestable)throwable ).printPartialStackTrace(out);
			} 
			else {
				throwable.printStackTrace(out);
			}
			return;
		}

		// generating the nested stack trace
		List stacks = new ArrayList();
		while (throwable != null) {
			String[] st = getStackFrames(throwable);
			stacks.add(st);
			throwable = ExceptionUtils.getCause(throwable);
		}

		// If NOT topDown, reverse the stack
		String separatorLine = "Caused by: ";
		if (!topDown) {
			separatorLine = "Rethrown as: ";
			Collections.reverse(stacks);
		}

		// Remove the repeated lines in the stack
		if (trimStackFrames) trimStackFrames(stacks);

		synchronized (out) {
			for (Iterator iter=stacks.iterator(); iter.hasNext();) {
				String[] st = (String[]) iter.next();
				for (int i=0, len=st.length; i < len; i++) {
					out.println(st[i]);
				}
				if ( iter.hasNext() ) out.print(separatorLine);
			}
		}
	}

	/**
	 * Captures the stack trace associated with the specified
	 * <code>Throwable</code> object, decomposing it into a list of
	 * stack frames.
	 *
	 * @param t The <code>Throwable</code>.
	 * @return  An array of strings describing each stack frame.
	 * @since 2.0
	 */
	protected String[] getStackFrames(Throwable t) {
		StringWriter sw = new StringWriter();
		PrintWriter pw = new PrintWriter(sw, true);

		// Avoid infinite loop between decompose() and printStackTrace().
		if (t instanceof Nestable) {
			( (Nestable) t ).printPartialStackTrace(pw);
		} 
		else {
			t.printStackTrace(pw);
		}
		return ExceptionUtils.getStackFrames( sw.getBuffer().toString() );
	}
    
	/**
	 * Trims the stack frames. The first set is left untouched. The rest
	 * of the frames are truncated from the bottom by comparing with
	 * one just on top.
	 *
	 * @param stacks The list containing String[] elements
	 * @since 2.0
	 */
	protected void trimStackFrames(List stacks) {
		 for (int size=stacks.size(), i=size-1; i > 0; i--) {
			 String[] curr = (String[]) stacks.get(i);
			 String[] next = (String[]) stacks.get(i-1); 
             
			 List currList = new ArrayList( Arrays.asList(curr) );
			 List nextList = new ArrayList( Arrays.asList(next) );
			 ExceptionUtils.removeCommonFrames(currList, nextList);

			 int trimmed = curr.length - currList.size();
			 if (trimmed > 0) {
				 currList.add("\t... "+trimmed+" more");
				 stacks.set(
					 i, 
					 currList.toArray(new String[currList.size()])
				 );
			 }
		 }
	 }
}
